When we lex an invalid leftbound dot, instead of emitting an error and swallowing it

silently, have the lexer return it as an unknown token.  Enhance the expr parser to
detect these things and squash any expression in progress into an ErrorExpr.  This
allows us to silence really bad downstream errors.  For example, on:

struct S { func f() {} }
func f() {
  _ = S.
}

we formerly produced:

 x.swift:5:8: error: expected member name following '.'
 x.swift:5:7: error: expected member name or constructor call after type name
 x.swift:5:7: note: add arguments after the type to construct a value of the type
 x.swift:5:7: note: use '.self' to reference the type object

we now emit just the first one.  This fixes:
<rdar://problem/22290244> QoI: "UIColor." gives two issues, should only give one

Author: lattner

lib/Parse/Lexer.cpp

@@ -755,8 +755,7 @@ void Lexer::lexOperatorIdentifier() {
 
       // Otherwise, it is probably a missing member.
       diagnose(TokStart, diag::expected_member_name);
-      //return formToken(tok::unknown, TokStart);
-      return lexImpl();
+      return formToken(tok::unknown, TokStart);
     }
     case '?':
       if (leftBound)

lib/Parse/ParseExpr.cpp

@@ -1392,7 +1392,7 @@ ParserResult<Expr> Parser::parseExprPostfix(Diag<> ID, bool isExprBasic) {
     // FIXME: Better recovery.
     if (Result.isNull())
       return Result;
-
+    
     // Check for a .foo suffix.
     SourceLoc TokLoc = Tok.getLoc();
     if (consumeIf(tok::period) || consumeIf(tok::period_prefix)) {
@@ -1618,6 +1618,16 @@ ParserResult<Expr> Parser::parseExprPostfix(Diag<> ID, bool isExprBasic) {
       consumeToken(tok::code_complete);
       return makeParserCodeCompletionResult<Expr>();
     }
+    
+    // If we end up with an unknown token on this line, return an ErrorExpr
+    // covering the range of the token.
+    if (!Tok.isAtStartOfLine() && consumeIf(tok::unknown)) {
+      Result = makeParserResult(
+                                new (Context) ErrorExpr(Result.get()->getSourceRange()));
+      continue;
+    }
+    
+    // Otherwise, we don't know what this token is, it must end the expression.
     break;
   }
 

test/IDE/complete_type.swift

@@ -131,7 +131,6 @@
 
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=TYPE_IN_STRUCT_INHERITANCE_4 > %t.types.txt
 // RUN: FileCheck %s -check-prefix=WITH_GLOBAL_TYPES < %t.types.txt
-// RUN: FileCheck %s -check-prefix=GLOBAL_NEGATIVE < %t.types.txt
 
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=TYPE_IN_STRUCT_INHERITANCE_5 > %t.types.txt
 // RUN: FileCheck %s -check-prefix=WITH_GLOBAL_TYPES < %t.types.txt
@@ -147,7 +146,6 @@
 
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=TYPE_IN_STRUCT_INHERITANCE_8 > %t.types.txt
 // RUN: FileCheck %s -check-prefix=WITH_GLOBAL_TYPES < %t.types.txt
-// RUN: FileCheck %s -check-prefix=GLOBAL_NEGATIVE < %t.types.txt
 
 
 // RUN: %target-swift-ide-test -code-completion -source-filename %s -code-completion-token=TYPE_IN_CLASS_INHERITANCE_1 > %t.types.txt

test/Parse/recovery.swift

@@ -405,7 +405,6 @@ struct MissingInitializer1 {
 
 func exprPostfix1(x : Int) {
   x. // expected-error {{expected member name following '.'}}
-    // expected-warning @-1 {{expression of type 'Int' is unused}}
 }
 
 func exprPostfix2() {
@@ -424,7 +423,7 @@ class ExprSuper1 {
 
 class ExprSuper2 {
   init() {
-    super. // expected-error {{expected member name following '.'}} expected-error {{expected '.' or '[' after 'super'}}
+    super. // expected-error {{expected member name following '.'}} 
   }
 }
 
@@ -651,7 +650,6 @@ func postfixDot(a : String) {
   _ = a.   utf8  // expected-error {{extraneous whitespace after '.' is not permitted}} {{9-12=}}
   _ = a.       // expected-error {{expected member name following '.'}}
     a.         // expected-error {{expected member name following '.'}}
-  // expected-warning @-1 {{expression of type 'String' is unused}}
 }
 
 // <rdar://problem/23036383> QoI: Invalid trailing closures in stmt-conditions produce lowsy diagnostics
@@ -664,3 +662,9 @@ func r23036383(arr : [Int]?) {
   }
 }
 
+// <rdar://problem/22290244> QoI: "UIColor." gives two issues, should only give one
+func f() {
+  _ = ClassWithStaticDecls.  // expected-error {{expected member name following '.'}}
+}
+
+

test/Sema/diag_values_of_module_type.swift

@@ -95,13 +95,13 @@ func badTest2() {
   _ = x
 }
 func badTest3() {
-  var _ = Swift. // expected-error {{expected member name following '.'}} expected-error {{expected module member name after module name}}
+  var _ = Swift. // expected-error {{expected member name following '.'}}
 }
 func badTest4() {
   _ = Swift // expected-error {{expected module member name after module name}}
 }
 func badTest5() {
-  _ = Swift. // expected-error {{expected module member name after module name}} expected-error {{expected member name following '.'}}
+  _ = Swift. // expected-error {{expected member name following '.'}}
 }
 func badTest6() {
   _ = { () -> Int in